Management Detail

Winter Moth/Bruce Spanworm

Winter Moth and Bruce Spanworm are two very closely related species. They have seldom been identified as an economic pest in blackberries but their feeding habits are such that it is difficult to assess their impact. Larvae appear in late winter/early spring before leaf break and can cause damage by feeding on the buds and thereby reducing yield. They are an occasional pest in raspberries. They can cause much more serious damage in blueberries. Feeding damage caused after leaf break is superficial. Larvae have pupated and are not present in the field by harvest so they are not a harvest contaminant.

The male flight takes place in November and December. A pheromone to monitor this flight is available only from a source in Eastern Europe.

Watch for single strands of spider web-like threads appearing in the branches in late February to March that comes from newly hatched larvae.

In early spring, closely monitor flower buds, clusters, and leaves for evidence of feeding and/or larval presence. Larvae are light to dark green caterpillars with two distinct white lines running the length of their bodies. Much larger than leafroller larvae, they react much less when agitated.

In fields with a history of winter moth problems, a late winter dormant oil and insecticide tank mix is often used to prevent re-occurrence of the damage.